Formula One drivers feel the G-force

Why g-force is the greatest pressure Formula One drivers have to cope with.

The Formula One world championship season resumes in Spain this weekend at Barcelona's Circuit de Catalunya, renowned for its proliferation of long, fast corners. It's a track that places exceptional loads on man and machine.

As well as a huge and sustained toll on their mental faculties, courage and general fitness levels, for two hours tomorrow afternoon drivers will frequently be exposed to a pressure that will never be experienced by most spectators: g-forces of a kind that would push ordinary mortals to the verge of lapsed consciousness.

G-force is the pressure that gravity exerts on an object when it is accelerating relative to freefall - and grand prix drivers are extraordinary athletes who can withstand these stressful forces while making crucial, split-second decisions.

Imagine trying to make a lightning-quick manoeuvre while upside down on a roller coaster when there are other roller coasters on the same track…

Motorsport's g-force spectrum ranges from 2g - a high-speed corner in a sports car, perhaps - to the 5.3g of a top-fuel dragster, which can accelerate from 0-100mph in less than a second.

There are a few examples of drivers surviving momentarily colossal g-forces, too. During practice for the 1977 British Grand Prix at Silverstone, for instance, David Purley was briefly exposed to a force estimated at 179.8g after his throttle stuck open at Becketts Corner.

In the subsequent impact, his car decelerated from 108mph to zero in a distance of little more than two feet. He suffered serious leg, hip and pelvic injuries, but recovered to race again.

Even in ordinary grand-prix races, F1 remains the blue riband of g‑force and drivers cope with 3-5g throughout each race. Paul Monaghan, head of car engineering for F1 team Red Bull Racing, says: "The predominant accelerative forces experienced by a driver are lateral and longitudinal, with the peaks exceeding 4.5g. The driver's body will experience forces four and a half times his or her own weight, albeit for short periods of time."

Fighter and aerobatic pilots withstand higher levels of g, but only on a vertical axis, and driving can create tougher g pressures for the body. "Military pilots experience greater g loads," Monaghan says, "but these are typically aligned with the spine, whereas an F1 driver endures these loads almost at right angles to the spine."

One of Monaghan's drivers is chiselled Australian Mark Webber, who says: "G-force makes it feel as though your body is being squeezed. In a fast corner the g-force comes on laterally as we go around, so your ribs, hip and neck get squeezed into the edge of the seat. You've got to get used to that. The force comes on slowly and peaks in the middle of the corner."

But when you hit the brake pedal, the g levels soars up and down. "That feeling is completely different," Webber says. "You hit the brakes very, very hard, so the g‑force is extremely high but goes away quickly."

Breath control is crucial - you cannot breathe freely above 3g because to do so would expose you to the risk of passing out. To prevent blood leaving your brain, you have to tense up.

"When you're experiencing g-force it can be hard to breathe normally," Webber says, "especially in a long, fast corner. It can make you a bit weaker because sometimes you have to hold your breath. You need to be strong to cope."

It demands incredible core fitness, stamina and concentration - though people can have wildly different g‑force tolerances. An obese man might have better g fitness than someone lean and fit, because his circulation limits his blood flow. The flip side, of course, is that he is more likely to keel over at the controls because of a heart attack.

Cardiovascular training only gets you so far, though, and you have to build up tolerance at the wheel. "In terms of training," Webber says, "the car's the best tool we have."

In the world of flying, there are few more g-resistant heroes than British aerobatic champion Nigel Lamb, who competes for Breitling in the Red Bull Air Race series, the F1 of the skies.

From flying helicopters in the Forces to fighting 12g in his experimental MXS plane, 53-year-old Lamb has a healthy respect for the forces to which he's exposed. "They really take it out of you if you are not used to it," he says, "and even I do not enjoy the feeling of g in a centrifuge machine."

I have first-hand experience of his aerial prowess after a spin in the Breitling MXS at High Wycombe airfield. First he took us to 3g with a slow roll and I was a little perturbed at how much I felt - it was definitely uncomfortable.

Then we stalled, pitched and looped the loop… before repeating the sequence at high speed. He told me to tense my calves and hold my breath. My neck jerked back and at 5g it felt as though my head was underwater, fighting a strong current.

Lamb spoke coolly (while we were pulling 5g, if memory serves). "The first thing to go is your eyes," he said. "When the world starts to turn grey you reduce the g - it all becomes instinctive. It is harder to withstand downward g - it's possible to get a redout at minus 2g."

Redout? That's when your head is swamped with blood.

Then he showed me a 7g move, the triple avalanche, a loop with a treble-flick roll and a high-speed spin. I had no idea what was happening - I just felt violence all over my body - and he subjected me to it for five seconds. I tensed all over and let out small breaths, but my vision tunnelled and curtains came over my eyes.

I all but blacked out just before we came through it. I think my face aged 20 years. It was extraordinary to feel such a great force. I was just glad I didn't sneeze: that would have added another 3g…

Still, if you think that's tough you should contemplate the resilience of a fly that has repeatedly been swatted with your copy of Motoring. Insects don't have a circulatory system, so they are masters at enduring g-forces because of the mechanical stresses their bodies can absorb. A fly can happily cope with 200g and froghopper bugs accelerate with twice that much force when they jump.